Removing paint



Patented Jan. 21, 1930 uNIrEo STATES PATENT OFFICE,

JAMES H. GRAVELL, OE ELKINS PARK, PENNSYLVANIA, ASSIGHOR T0 AMERICAIhT DE AWARE No Drawing.

This invention relates generally to the removal of paint, oil, varnish, lacquer, japan of the invention to economize labor, time,

heat and floor space, and generally to improve the art.

Although the invention may be applied generally to removing paint, it is particularly applicable to the removal of asphaltic j apans, commonly called high baked black enamel fiipm steel automobile bodies, fenders and the li e.

According to the prior art as known to me as being in practical use, the object from which the paint is to be removed is boiled in an aqueous solution of sodium hydroxide for a period ranging from a few minutes to a number of hours, according to the quality and hardness of paint. is made by adding' the sodium hydroxide to a heated bath of water, in which it dissolved with such violence that portions of the liquid are often thrown from the vat to the great danger of the attendants. Some kinds of paint are entirely removed by the bath, Whereas other varieties, such as hard baked gilsonite enamels, are only loosened and must be mechanically removed or scraped after the work is withdrawn from the bath.

I have discovered that if cresylic acid, which is one of the phenols of which others are carbolic acid, varieties of cresylic acid and a number of other materials, is added to the caustic bath the time required to remove the paint is materially shortened and in cases where the paint is only loosened, the

labor of mechanically removing it is greatly reduced or entirely eliminated.

Application filed June 22,

The aqueous solution -'GHMIGAL -PAINT COMPANY, OF AMBLER, PENNSYLVANIA, A CORPORATION OF REMOVING PAINT 192s. SerialNo. 117,878.

I have further discovered that excellent results are obtained when the sodium hydroxide and the cresylic acid are definitely proportioned so that for every ten pounds of sodium hydroxide (98%) there are used about two and a half pounds of cresylic acid (98%).

I have further found that chemical equivalents, such as phenols, cresols and xylenols, may be used in place of cresylic acid (which is one of the phenols) and that any suitable caustic may replace the sodium hyroxide, but I consider caustic soda (sodium hyroxide) and cresylic acid to be the best and cheapest selection from a commercial standpoint.

To make up a suitable bath according to my invention I may use:

Pounds Water 700 Sodium hydroxide 250 Cresylic acid 70 p The ingredients are preferably added in the order given and produce a bath of about 200 gallons. The cresylic acid immediately combines with the sodium hydroxide to form what I term sodium cresylate but as there is more than enough sodium hydroxide present to complete the reaction an excess of sodium hydroxide is left behind, thus producing an aqueous bath in which are dissolved sodium cresylate and sodium hydroxide.

To remove paint according to my invention I maintain the bath at about 180 F. and immerse the object from which the paint is to be removed. I allow the object to remain in the bath until the paint is removed, or in the case of baked black enamel, until the painted coating loosens, when I withdraw it and thoroughly wash it with water, preferably applied lute acid, preferably phosphoric acid, thus,

neutralizing all alkalinity.

Under similar conditions my bath will remove the painted finish in about one fifth of the time required by a straight caustic soda bath, and the work n'oduced does not have to be scraped by hand in order to remove adhering particles as they have been so loosened that the water entirely removes them during the washing operation.

If the object from which the paint has been removed is steel, the surface produced by my remover and process is superior to that reduced by the straight caustic soda bath, ecause it is not tarnished, and as no scraping is required to remove adhering particles, it is not-marred by scratches.

For convenience I may supply my remover in paste form, consisting of:

Pounds \Vater 280 Sodium hydroxide 250 This paste may be added to water, heated nearly to boiling, in any desired proportion depending on the strength required and may vary up to 12 pounds of my paste to the gallon of water. As but little heat is generator by the solution of my paste in water, the sudden generation of steam with its accompanying violent ebullition is avoided and the usual danger of adding caustic to heated water is consequently, eliminated.

In case I desire to supply my remover as a dry material, I modify my formula to Cresylic acid P nd Dry sodium hydroxide (98%) 3256 Cresylic acid (98%) 70 It is best to use sodium hydroxide and to thoroughly mix the cresylic acid with it in order to secure a uniform compound free from lumps. The sodium hydroxide acts on the cresylic acid converting it to solid sodium cresylat-e, and as there is an excess of sodium hydroxide present, the ultimate material is a dry admixture of sodium hydroxide and sodium cresylate.

As my remover operates at high speed the number of vats required for a given amount of work may be proportionally reduced, thus saving floor space, and heat and working schedules may be worked out so that no time is lost in waiting for the processed work and hence labor may be economized.

In cases where the shape, size or construction of the object to be stripped, makes it unsuited to the immersion method, such as a steel automobile body constructed with a wooden frame, I may apply my cleaner to the object in the form of a thin heated stream, progressing from one spot to another as the paint is removed.

It will be obvious to those skilled in the art that modifications may be made in details of procedure and in matters of mere form withoutdeparting from the spirit of the invention, which being chemical in its nature is entitled to the doctrine of equivalents appropriate in such cases. I therefore do not intend to limit the invention otherwise than as the prior art and the appended claims may require.

I claim 1. The method of removing high baked black enamels from the surface of steel automobile bodics and parts, which consists in immersing them in a bath at a temperature of substantially 180 F. and containing anadmixture of water, about 700 pounds, and sodium hydroxide, about 250 pounds, and cresylic acid, about 70 pounds, until the coating of enamel loosens, and then removing the article from the bath and washing it with a high pressure stream of water to remove all the loosened particles.

2. The method of refinishing painted surfaces, consisting in loosening the old paint by the action of an admixture, ingredients of which are sodium cresylate and sodium hydroxide, removing the loosened paint and the admixture, subjecting the surface thus obtained to the action of phosphoric acid, drying the surface to fit it for repainting.

JAMES H. GRAVELL. 

